| A | B |
|---|
| blastula | hollow, fluid-filled ball of cells |
| gastrula | an indention in the blastula |
| protostome | mouth from gastrula indention |
| dueterostome | mouth not from gastrula indention |
| ecotoderm | outer layer of tissue; skin and nerves |
| endoderm | inside layer of tissue; digestive system |
| mesoderm | middle layer of tissues; muscles |
| sessile | fixed in once place |
| endoskleton | internal skeleton |
| exoskeleton | external skeleton |
| vertebrate | has a backbone |
| invertebrate | no backbone |
| coelomate | fluid-filled body cavity completely lined with mesoderm |
| pseudocoelomate | fluid-filled body cavity partially lined with mesoderm |
| acoelomate | no fluid-filled body cavity |
| asymmetry | no way to make identical portions |
| bilateral symmetry | can only be cut along one plane to make identical halves |
| radial symmetry | can be cut along any plane that runs though a central axis to make identical halves |
| dorsal | the " back" part |
| ventral | the "front" part |
| anterior | the "top" part |
| posterior | the "bottom" part |
